The present invention relates to a remote engine starter system and pertains, more particularly, to an improved tachometer apparatus employed in such an engine starter system.
A remote engine starter system typically includes, inter alia, a tachometer to sense the proper operation of the engine. The tachometer may be coupled to control circuitry for controlling operation of the remote engine starter system.
One example of the use of a tachometer in a remote automobile starter is found in U.S. Pat. No. 5,024,186 to Long et al. It is noted in this patent that they provide an inductive pick-up arrangement that clamps around any one of the spark plug wires coming from the distributor. This inductive pick-up has a coil of wire with one side going to ground and the other side going to the remote automobile starter unit at the tach input thereof. This inductive pick-up outputs a pulse every time a sparkplug fires.
Another tachometer arrangement employs a sense wire to the ignition coil. This requires a specific tachometer wire and an extra sense line.
In older remote controlled engine starter systems, vacuum switches operatively connected to the engine""s intake manifold were used to detect that the engine was running. Magnetic sensors mounted in the engine""s flywheel have also been used to determine engine speed.
In the above examples it is noted that separate hard wiring is required to certain engine components such as an ignition coil or a spark plug. This extra wiring can be problematic and is time consuming to install in vehicles.
Accordingly, it is a purpose of the present invention to provide an improved tachometer apparatus for use with a remote engine starter system that does not require extra wiring and that is characterized by a simple installation on a wide variety of vehicles.
According to the invention, there is provided a tachometer apparatus for providing tachometric information to a controller of a remote vehicle starting system. The controller is remotely activated to initiate a starting of the vehicle engine. The tachometer apparatus in accordance with the invention comprises an antenna disposed proximate to the engine compartment of the vehicle and adapted to pick-up an RF signal generated by the firing of the spark plugs in the engine compartment. The apparatus further comprises an RF detector having the antenna coupled to the input thereof and providing at its output a tachometer signal for coupling to the controller and providing a signal indicative of the running status of the vehicle engine.
In a preferred embodiment of the present invention, the RF detector uses as an antenna the existing hood pin switch wire, which is usually a safety feature of a remote engine starter system. The hood pin switch sensor located in the engine compartment is used to monitor the opening of the hood to disable the remote engine starter if the hood is opened. The proximity of this to the engine cylinders and ignition system make it possible to us the hood sensor conductor line to pick up the RF signal generated by the firing of the spark plugs in the engine compartment. In other embodiments of the invention the antenna may be power lines that run in the engine compartment or, alternatively, one may dispose a separate antenna element in the engine compartment.
There is also provided, in accordance with the present invention, a method of generating tachometric information to a controller that is part of a remote vehicle starting system that may be remotely activated to initiate a starting of the vehicle engine. In accordance with this method there is the step of detecting an RF signal generated by the firing of the spark plugs in the engine compartment, followed by the step of generating a tachometer signal derived from the detected RF signal, coupled to the controller, and indicative of the running status of the vehicle engine.